A process for repairing the surface of coated substrates that involves
a) providing a substrate having a damaged surface,
b) coating a carrier sheet on one side with a layer of an uncured or part-cured coating material,
c) applying the carrier sheet by its coated side to the repair site,
d) fully curing the layer of the coating material with heat, and
e) removing the carrier sheet,
the layer of the coating material being heat-treated through the carrier sheet or following removal of the carrier sheet, is known from international patent application WO 03/092912. A similar process in which the layer of the coating material is cured with high-energy radiation, or UV radiation, is known from the American patent U.S. Pat. No. 6,743,466 B2.
European patent application EP 1 410 850 A2 discloses in general terms a similar process for producing coatings that involves fully curing the layer of the coating material likewise with heat.
European patent application EP 1 410 888 A2 discloses in general terms a similar process for producing coatings that involves fully curing the layer of the coating material with high-energy radiation, such as with UV radiation.
Although it is said, for example, in European patent application EP 1 410 888 A2, column 7, paragraph [0028], that the coating material may also include water, the examples of the three aforementioned patent applications and of the aforementioned American patent use only a coating material which comprises organic solvents and a urethane acrylate that is curable by free-radical polymerization, is free of acid groups, and has an olefinically unsaturated double bond content of 1.927 eq/kg.
The conventional coating materials, however, have the drawback that considerable volumes of volatile organic solvents are emitted in the course of the production of the coated sheets. This leads to safety and environmental problems for the manufacturer of the coated sheets. Any residues of volatile organic solvents that may still be present in the coated sheets, as well, may lead to comparable problems for the user, in the case, for example, of the refinishing of damaged automobile finishes in the painting workshop, for example.
It would therefore be desirable to have available, for repair purposes, coated sheets whose coatings can be produced from aqueous coating materials.
In the patent applications cited above, however, there are no details of what measures might be taken in order to provide aqueous coating materials which have the same profile of properties as the known, conventional coating materials, are suitable for the known refinish process, and produce coatings meeting all of the requirements that are imposed on automotive refinishes.